Assessment and management of amebiasis
ASSESSMENT
HISTORY AND PHYSICAL EXAMINATION ã…¡ Although most cases of amebiasis are asymptomatic, many patients with E. histolytica present with a spectrum of illness. The incubation period from amebiasis is between 2 to 4 weeks.
Symptoms range from mild abdominal cramps and watery diarrhea to severe colitis producing bloody diarrhea with mucus. Young people tend to have a more severe disease compared to older individuals. Fulminant colitis can present with bloody diarrhea in some patients. Risk factors include the use of corticosteroids, poor nutrition, young age, and pregnancy. Toxic megacolon can be a complication and is associated with very high mortality.
A few patients may develop invasive extraintestinal disease. The most common extraintestinal manifestations are an amoebic liver abscess. A liver abscess develops in less than 4% of patients and may occur within 2 to 4 weeks after the initial infection. Liver abscess usually presents with right upper quadrant pain, fever, and tenderness to palpation. An amoebic liver abscess may rupture into the pleural cavity or pericardium, presenting as pleural or pericardial effusion; however, this is a rare occurrence. Rarely, amebiasis may affect the heart, brain, kidneys, spleen, and skin. One can also develop proctocolitis, toxic megacolon, peritonitis, brain abscess, and pericarditis. Hence, amebiasis is a leading parasitic cause of death in humans.
DIAGNOSIS
LABORATORY TESTS ã…¡ Diagnosis is typically made by identifying organisms in the stool. Molecular diagnosis is possible from multi-pathogen panels, which are sensitive and specific, but expensive. E histolytica and E dispar cannot be distinguished, but identification of amebic trophozoites or cysts in a symptomatic patient is highly suggestive of amebiasis. In mild disease, microscopic hematochezia is common. In severe disease, leukocytosis and hematochezia, with fecal leukocytes not present in all cases.
MANAGEMENT
Fluid and electrolyte replacement is important for patients with significant diarrhea. Medications (see Table 1 below). Asymptomatic infection with E dispar does not require therapy. Intestinal colonization with E histolytica is treated with luminal agent such as diloxanide furoate (500 mg three times daily with meals for 10 days) or iodoquinol (diiodohydroxyquin; 650 mg three times daily for 21 days) or paromomycin (30 mg/kg base, maximum 3 g, in three divided doses after meals daily for 7 days). Side effects include flatulence with diloxanide furoate, mild diarrhea with iodoquinol and gastrointestinal symptoms with paromomycin.
Metronidazole (750 mg three times daily for 10 days) or tinidazole (2 g once daily for 3–5 days) plus a luminal agent is treatment of choice. However, tinidazole offers simpler dosing, a more rapid clinical response, and fewer side effects than metronidazole. Side effects of both agents include transient nausea, vomiting and epigastric discomfort and metallic taste. A disulfiram-like reaction may occur if alcohol is coingested. Tetracycline (250–500 mg four times daily for 10 days) plus chloroquine (500 mg/d for 7 days) can be used as alternative therapy.
Emetine or dehydroemetine can be given subcutaneously or intramuscularly in a dose of 1–1.5 mg/kg/day. Maximum daily doses for emetine, 65 mg and for dehydroemetine, 90 mg. These agents only used until severe disease is controlled because they are cardiotoxic with a narrow therapeutic range. Side effects include nausea, vomiting, pain at injection site.
| Table (1). Treatment of amebiasis | ||
|---|---|---|
| Clinical Setting | Drugs of Choice and Adult Dosage | Alternative Drugs and Adult Dosage |
| Asymptomatic intestinal infection | Luminal agent: Diloxanide furoate, 500 mg orally three times daily for 10 days or– Iodoquinol, 650 mg orally three times daily for 21 days or– Paromomycin, 10 mg/kg orally three times daily for 7 days |
|
| Mild to moderate intestinal infection | Metronidazole, 750 mg orally three times daily (or 500 mg intravenously every 6 hours) for 10 days or– Tinidazole, 2 g orally daily for 3 days plus– Luminal agent (see above) |
Luminal agent (see above) plus either– Tetracycline, 250 mg orally three times daily for 10 days or– Erythromycin, 500 mg orally four times daily for 10 days |
| Severe intestinal infection | Metronidazole, 750 mg orally three times daily (or 500 mg intravenously every 6 hours) for 10 days or– Tinidazole, 2 g orally daily for 5 days plus– Luminal agent (see above) |
Luminal agent (see above) plus either– Tetracycline, 250 mg orally three times daily for 10 days or– Dehydroemetine or emetine, 1 mg/kg subcutaneously or intramuscularly for 3–5 days |
| Hepatic abscess, ameboma, and other extraintestinal disease | Metronidazole, 750 mg orally three times daily (or 500 mg intravenously every 6 hours) for 10 days or– Tinidazole, 2 g orally daily for 5 days plus– Luminal agent (see above) |
Dehydroemetine or emetine, 1 mg/kg subcutaneously or intramuscularly for 8–10 days, followed by (liver abscess only) chloroquine, 500 mg orally twice daily for 2 days, then 500 mg daily for 21 days plus – Luminal agent (see above) |
FOLLOW-UP
Examine at least three stools at 2- to 3-day intervals, starting 2–4 weeks after the end of treatment. Colonoscopy and reexamination of stools within 3 months may be indicated.
REFERENCES
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Saidin, S., Othman, N. and Noordin, R. (2018). Update on laboratory diagnosis of amoebiasis. European Journal of Clinical Microbiology & Infectious Diseases, [online] 38(1), pp.15–38. Available at: https://link.springer.com/article/10.1007/s10096-018-3379-3
Stanley, S.L. (2003). Amoebiasis. The Lancet, [online] 361(9362), pp.1025–1034. Available at: https://www.sciencedirect.com/science/article/pii/S0140673603128309
Diagnostics, and Current Therapeutics for Amebiasis. Open Forum Infectious Diseases, [online] 5(7). Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6055529
